Electric furnace



G. MARS ET AL ELECTRIC FURNACE Jan. 24, 1%39.

Filed April 10, 1935 Patented Jan. 24, 1939 ELEGTRIC FURNACE Georg Mars, Csepel at Budapest, Hungary, and Richard Hirsch, Munich, Germany Application April 10, 1935, Serial No. 15,708 In Germany April 16, 1934 10 Claims. (0]. 13-26) The known coreless induction furnaces are in the material to be melted. In the case of uni'- operated by two-phase or multi-phase current. polar dynamo machines this voltage is taken by In order to increase the induction effect the opermeans of brushes to slip rings. If these slip rings ating current is caused to act in coils which are are closed by an external circuit then direct ourarranged over laminated iron cores. Furnaces rent is produced. of this kind have considerable disadvantages, the In the apparatus of the present invention the cost of installation, in particular, being very high. E. M. F. produced is used to produce currents, Further, high frequency furnaces require expenwhich are used up in the conductor itself in order sive condenser plants while line frequency furto heat the conductor, that is to say the current naces must be provided with a very large power is also to be consumed at the place where it is installation because the power factor is very low. produced.

An object of the present invention is to avoid In accordance with. a further feature of the these disadvantages. The invention enables ininvention, provision is also made so that the magduction furnaces to be operated with small and netic field does not extend uniformly over the inexpensive power installations without a source Whole of the material to be melted but that zon s of heavy current being necessary. In accordance are formed which are as free as possible from with the invention, the current necessary for the production of the heat for melting is not supplied to the furnace, as in the known furnaces, from the outside, but is produced in the material itself to be melted. In order to carry this novel idea into effect, provisionis made for the material to be melted to be permeated by a field of lines of magnetic force and a relative movement is caused to take place between the material to be melted and this field of lines of magnetic force. By this means induction currents, namely eddy currents, which heat the material are set up in the ma-- terial itself. By means of one or more pairs of rotary magnet poles alternating currents can be produced in the material itself having a frequency which is proportional to the speed of revolution of the poles. Further, by the arrangement of a unipolar magnet, a direct current can also be produced in the material. Either permanent magnets or electro-magnets can be employed. If electromagnets are employed they can be energized either by direct current or by alternating current or by a combination of both.

A further object of this invention is to provide for the melting of mixed materials in apparatus of this kind in a crucible having a unitary chamber adapted to hold the mixed material to be heated in a concentrated compact.

A furnace having a uni-polar magnet is particularly advantageous. This type of magnet enables an annular magnetic field or circuit in which the direction of the lines of force is similar to be produced. If the melting chamber be situated in the interior of the magnetizing coil the greatest density of the lines of force is produced in the melting chamber. If the magnetic field is rotated, a direct current voltage which always maintains its direction is produced in each conductor which the lines of force cut, that is to say from induction. By this means the formation of the currents which effect the heating within the material is considerably facilitated.

It has, moreover, been determined that it is possible to allow only a part of the magnets, for example the poles, to rotate and to allow the reentire winding to remain stationary. By this means the construction of the new furnaces is considerably simplified, since it is not then necessary to balance and move a heavy and complicated body.

Two preferred forms of construction of the new furnace are illustrated by way of example in the accompanying drawing, in which:--

Figure 1 is a vertical section through a unipolar furnace having a rotary magnetic casing and coil;

Figure 2 is a plan thereof;

Figure 3 is a longitudinal section through a furnace having two pole wheels rotating about horizontal axes, and

Figure 4 is a section in part along the line IV--,-IV. and in part along the line V-V of Figure 3.

Referring to Figures 1 and 2 of the drawing,

I which is revolubly mounted on the base plate 2, so that it can rotate about a vertical axis. The casing rests on the base plae through the intermediary of ball bearings 3 and is guided by means of a vertical stationary spindle 4 which also carries the crucible 5- having a unitary chamber adapted to hold the material to be heated in a concentrated body and is provided with a cover 6. The casing is provided with a belt pulley 1 by which it is driven from a motor 8 by means of a belt 9.

lines of force and, therefore, as free as possible maining parts of the magnetic casing and the the furnace consists of a pot-like magnet casing An annular coil III is arranged in the casing I. A core II which is provided with acentral bore projects into the coil and this core is either made in one piece with the casing or is in magnetic connection therewith. The magnetic casing is closed by. a cover plate l2 which is magnetically and mechanically connected thereto by means of bolts l3. A yoke l5 having an opening I6 is inserted in an aperture having conical. walls H which is provided in the cover plate i2. After the yoke plate has been removed the crucible f. can be lifted upwards, for example by means of a crane, which is not illustrated in the draw-ing.

The crucible is firmly connected to the stationary spindle 4, for example by means of a pin II but is capable of being removed. The yoke plate is rigidly connected with the cover plate. It is also provided with apertures l8 (see Figure 2) so that when seen from above it has the appearance of a spoked wheel. Opposite the spoke-like pole pieces l9 which form the one pole corresponding I v and 4 the magnet casing is constructed in the form of a drum having alhorizontal axis. The drum 20 encloses fromboth sides the hearth 2| which is of relatively narrow andhigh construc tion. It is provided with a charging and working opening 22.

which the hearth 2| is located are arranged in the magnet casing 20. The coils are connected in such a way that they form a uni-polar magnet. In this furnace the casing 20 and the coils 24, as well as the hearth 2|, remain stationary during operation. Only the pole wheels rotate, being mounted for this purpose on axes 25 and driven for example directly from motors which are not illustrated and are connected to the couplings 21. Each pole wheel 25 is provideti with pole pieces 28 which cover only part of the adjacent faces of the chamber and extend into proximity to the chamber in a similar manner and similar purpose as pole pieces l9 and 30 in Figs. 1 and 2 as dcscribed-above. either in the same direction .or in. opposite directions.

The hearth 2! is constructed in such a manner that it can be illled up to the level 28 so that a part of the melting bath lies above the magnetic field which is formed between the two pole wheels. These upper layers have a dampl'ngleflect on the tendency of the melting bath -to follow the rota tion .of the'magnetic field. w

What we claim is:-'-

1. In aninduction furnace, astationary mage net system, a relatively narrow and high crucible adapted to be filled to such an extent'that a part of its contents lies outside the magnetic field of said magnet system, said system comprising two pole wheels rotatable about a horizontal axis on each side of the crucible,and poles arranged on said pole wheels and rotatable therewith.

,2. In an electric furnace, a crucible having a unitary chamber adapted to hold the material in In order to be able to tilt the furnace, it is mounted on rollers 23. Two coils 24 between The pole wheels 25 can be rotated a concentrated body, a magnet system, said system comprising a stationary magnet and rotatable poles for directing concentrated magnetic flux'through said crucible chamber, and means for rotating said poles relative to the crucible chamber.

3. In-an electric furnace, a crucible having a unitary chamber adapted to hold the material in a concentrated body, a magnet system including a stationary magnet'and a rotatable pole, said pole being located adjacent the crucible for directing concentrated magnetic flux through the crucible chamber, said' pole having projecting pieces providing non-uniformity of concentrationof the flux passing through said chamber, and

means for rotating said ,pole relative to said crucible chamber to produce non-uniform electrical potential'in the materialin the crucible chamber.

4. In an electric furnace, a crucible having a unitary chamber adapted to hold the material in a concentrated body, a magnet system, said magnet system including poles o'fdissimilar polarity disposed on opposite sides of the crucible chamber for directing concentrated magnetic flux through the cruciblechamber, said poles having projecting parts extending toward the crucible for providing non-uniformity of concentration of the fiuxpassing through the crucible, the projecting parts of each pole being of similar pola ity, and means for rotatingsaid poles.

5. In an electric furnace, a crucible having a unitary chamber adapted .to hold the material. in

a concentrated body, a magnet system, said magnet system. including a stationary magnet, and

poles of dissimilarpolarity disposed on opposite sides of the crucible chamber for directing concentrated magnetic flux through the. crucible chamber, said poles having pieces projecting toward the crucible, adjacent pieces of each pole being of similar polarity, and means for rotating the poles. 1

6. In an electric furnace, a crucible having .a unitary chamber adapted to hold the material in a concentrated body, a magnet systemfsaid magnet system including a stationary magnet, and poles of dissimilar polarity disposed on opposite sides of the crucible chamber for directing concentrated magnetic flux through the crucible chamber, the faces of said poles toward thecrucible having openings formed therein for providing non-uniformity of concentration of the flux passing through the crucible, and means for rotating said poles, whereby movement of the non-uniform flux with respect to the material to be heated in the crucible generates non-uniform electrical potential in said material and the material is heated by the heat of. resistance to'the flow of current produced by said potential.

'7. In an electric furnace, a crucible having a relatively narrow and high unitary chamber adapted to hold the material to be heated in a concentrated, compact body, a magnet system com,-

prising a'stationary magnet, and a pair of IOtat-w trated magnetic flux, and means for rotating the,

poles.

8. In an electric furnace, a cruciblehaving a single unitary chamber adapted to hold the ma-'- terial to be heatedin a concentrated body, a

magnet system having a circuit. of magnetic material. provided with a gap, said chamber being of the body of material having portions extendlocated in said gap, said magnetic circuit ineluding magnetic conductors on opposite sides augaae ing into closer proximity to the chamber than other portions for producing non-uniformity of magnetic flux in the material in said crucible chamber, and means for moving said conductors relative to said crucible chamber and the material contained therein to produce non-uniform electrical potential in the material in the crucible chamber whereby said material is heated by local flow of eddy currents from points of high potential to points of low potential in the material.

9. In an electric furnace, a crucible having a single unitary chamber adapted to hold the material to be heated in a concentrated body, a rotatable magnet system including a circuit of magnetic conducting material provided with a gap, said chamber being located in said gap, said circuit including pole pieces extending only partially over opposite sides of the crucible and in proximity thereto for producing non-uniformity of the magnetic flux in the material in said crucible, and means for rotating said pole pieces relative to said chamber to move the magnetic flux relative to the material to be heated in the chamber to produce non-uniform electrical potential in the material whereby the material is heated by local flow of eddy currents from points of high potential to points oi. low potential in the material.

10. In an electric furnace, a crucible having a unitary chamber adapted to hold the material in a concentrated body, a rotatable magnet system having a circuit of magnetic material provided with a gap, said chamber being located in a said gap, said circuit having pole pieces adjacent the chamber extending only partially over a side or the chamber and into proximity thereto for producing non-uniformity of magnetic flux in the material in said crucible, adjacent pole pieces being of similar polarity, and means for rotating said magnet system relative to said chamber to move the non-uniform magnetic flux relative to the material to be heated to produce non-uniform electrical potential in the material in the crucible chamber and eddy currents, the resistance otflow of which heats the material.

GEORG MARS. RICHARD HIRIfCH. 

